12 things to know about cannabis and mental health

It’s the most common illicit drug in Australia

Cannabis is the most widely used illegal recreational drug in Australia and is increasingly attracting attention for its potential medicinal benefits. But there remain many questions about its impact on the brain and the role it plays in mental health. A leading drug researcher, Val Curran, a Professor of Psychopharmacology at University College London, says that understanding this link is more important than ever as illicit users increasingly report issues arising from its use.

Addiction is increasing

Professor Curran, a recent professorial fellow at Australian Catholic University and a co-founder of the independent charity Drug Science, says: “What’s a pressing problem these days – and it didn’t use to be such a problem – is addiction, which affects one in nine users.”

The chemistry is complex

Cannabis contains more than 100 different types of cannabinoids, which are the chemicals that provide the pleasant affects that users report plus medicinal benefits, such as pain relief. One of these, THC, is the cannabinoid that provides the ‘high’, while CBD counteracts this side effect. Professor Curran says: “CBD offsets the negative side effects of THC, so if your cannabis has high levels of CBD, then you’re less likely to develop a psychotic disorder, and you’re much less likely to become addicted”.

Higher THC is causing problems

That balance has altered dramatically in recent years, as strains of cannabis with higher THC are being cultivated and sold, contributing to increasing rates of addiction among users. Just a few years ago, cannabis was commonly sold with about eight per cent THC; today, it’s closer to 15 per cent. In some countries some strains of cannabis have 20 per cent THC. “It’s gone up hugely, and it’s because of money. The stronger the cannabis is, the more dealers can charge for it,” Professor Curran says.

Experiences vary

Different users experience cannabis in different ways, she says. Some of these symptoms include slower thinking and reflexes, depression, reduced motivation, delusions, panic attacks, anxiety and paranoia, hallucinations and psychosis. Long-term users are also at higher risk of suicide attempts.

Your genes might matter

The younger a user is, Professor Curran says, the more likely they are to experience psychosis, but genetics and family history also play a big role. “There’s something called the AKT1 gene that seems to play in role in more vulnerable people becoming addicted, and we know that psychosis is also genetically influenced. But the vast majority of people who smoke cannabis don’t end up having mental health problems.”

The younger, the more vulnerable

Teenagers respond differently to cannabis than adults, Professor Curran explains, saying that it makes them more impulsive. “Younger users don’t get satiated with it, they want more and more, whereas adults will get satiated with it more easily, and become less impulsive. They also experience less negative psychological effects.”

A new study is underway

In a bid to find out more about cannabis and mental health, Professor Curran is undertaking a four-year study of adolescents and adults who use cannabis, and the impact this has on their brains. This world-first study, which has attracted funding from the UK’s Medical Research Council, will analyse why the drug effects differ for adults and adolescents. Professor Curran and her team will scan participants’ brains and also examine mental health measures, memory and school achievement.

Medical potential is promising

Some Australian states have now legalised medical cannabis, especially for use in children with severe epilepsy and other debilitating chronic illnesses. Multiple reports and anecdotal evidence have confirmed its benefits in drastically reducing symptoms, including seizures and chronic pain. “Cannabis is potentially a medicine chest, it has so many different cannabinoids and it offers new ways to treat illness,” she says. “There is some evidence that cannabidiol could also treat schizophrenia.”

Legalisation is under discussion

Medical use and recreational use, however, are two distinctive things, with different strains of cannabis providing different benefits and harm. Eight states in the US have legalised recreational cannabis use, the Netherlands, Spain, Uruguay and Canada have also legal exemptions for recreational and personal use. The debate about legalising cannabis for recreational use in Australia is likely to continue.

Further research is required

Associate Professor Melissa Norberg MAPS from Macquarie University researches problematic cannabis use and its treatment. In a commentary in The Lancet she recently noted the difficulty of measuring quantity consumed, when past research has focused frequency of use. “With alcohol we have a standard drink unit and it allows us to determine safe and unsafe levels of use. Because cannabis purchases are not regulated, any given cone or joint can vary in amount and strength,” she says. “Before we can have a discussion about legalisation, we need to develop a standardised unit of cannabis to assist us in determining if cannabis is safe and at what levels.”

Education is key

For now the focus needs to be on informing users about the risk of harm. “I think people need educating, especially people who are vulnerable,” Professor Curran says, of the mental health risks.